Hydraulic clutch control, notably for motor vehicles

ABSTRACT

Hydraulic clutch control, having a clutch release fork (25), a control member (8) capable of acting in traction on the clutch release fork (25), a hydraulic receiver (1) having a fixed cylinder (2) mounted on a counter-support (5) and a piston (4) engaged so as to slide sealingly in the cylinder (2) and defining therein a chamber (6). The control member (8) enters inside the piston (4) of tubular shape like the cylinder (2). This member is mounted in an articulated manner on the fork (25) and on the back end of the piston.

The present invention concerns clutch controls and more particularlyhydraulic clutch controls, notably for motor vehicles.

As is known, a clutch release control has (FIG. 1) a clutch release fork25 capable of being mounted pivoting on a fixed support such as thehousing of a gearbox.

This fork 25 cooperates with a clutch release bearing 26 which, whenactuated, is adapted to stop the elastic compressing action of anelastic diaphragm 27 on a thrust plate 28 of a friction clutch 29, ofwhich a reaction plate 30 and friction disc 31 can be seen.

The means for tilting the diaphragm 27 on a cover 30A fixed to the plate30 are depicted at 27A.

For the record, it should be stated that the clutch is normally engaged,the friction linings of the friction disc 31 being gripped between thereaction plate 30 and thrust plate 28 under the action of the elasticload exerted by the diaphragm 27.

In order to disengage the clutch, it is necessary to act here by pullingon the clutch release fork 25 in order to make it tilt and to move theclutch release bearing 26 to the left of FIG. 1 in order to make thediaphragm 27 pivot and to cancel the load exerted by the said diaphragmon the thrust plate 28 in order to release the friction disc 31.

Here the control of the clutch release fork is effected with the aid ofa cable 101 actuated by the clutch pedal.

It was proposed in the document DE-A-42 20 020, notably for reasons ofcomfort, that the cable control be replaced by a hydraulic control.

This hydraulic control has a hydraulic receiver having a fixed cylindermounted on a counter-support fixed to a fixed support of the vehicle anda piston engaged so as to slide sealingly in the cylinder in order todefine therein a chamber of variable volume connected to a transmittercontrolled by the clutch pedal.

In this document, the piston rod constitutes a control member capable ofacting in traction on the clutch release fork, being mounted in anarticulated manner on the said fork by means of a drive bearing.

In this type of control, the clutch release fork, when operated, effectsa movement in an arc of a circle whilst the piston moves in arectilinear manner, so that the cylinder is mounted on a counter-supportfixed to the fixed support by means of a bearing made of elasticmaterial in order to compensate for the pendular movement of the rod.This arrangement complicates the control and is not optimal in respectof the freedom of movement of the piston. In addition, it leads to aloss in efficiency owing to the presence of the elastic bearing.

The object of the present invention is to overcome these drawbacks.

According to the invention, a hydraulic control of the type indicatedabove is characterised in that the cylinder is of tubular shape, in thatthe piston is of tubular shape and has at a back end a guidingprojection designed to cooperate with the internal bore of the cylinderand directed radially outwards, whilst the cylinder has at a front end aguiding projection designed to cooperate with the outer periphery of thepiston and directed radially inwards, and in that the control memberenters inside the piston of the receiver and is mounted at one of itsends in an articulated manner on the clutch release fork and at theother end so as to articulate on the back face of the piston of thehydraulic receiver.

According to one embodiment the control member is a cable acting betweentwo bearings coupled respectively to the back face of the piston and tothe clutch release fork.

In a variant, a rod is mounted so as to articulate on the clutch releasefork and at the other of its ends so as to articulate on the back faceof the piston.

By virtue of the invention, the piston is pulled by means of a cableconnected to the clutch release fork or by means of a rod mounted so asto articulate on the piston and on the clutch release fork, in order totake into account the kinematic differences between the movement of theclutch release fork in an arc of a circle and the rectilinear movementof the piston.

It will be appreciated that the small movement of the control member inan arc of a circle is due to the fact that it is mounted so as toarticulate at the rear of the piston. The movement of the control memberis of a smaller amplitude than if it had been mounted at the front ofthe piston.

Thus, jamming of the piston is prevented in a simple and economicalmanner. In addition, it is possible to mount the cylinder of thereceiver fixedly on the counter-support, enabling the efficiency of thecontrol to be improved as there is no elastic bearing to compress as inthe prior art.

In addition, it is simple to house a spring in the control chamber, thesaid spring acting between the two guiding projections in order to pullon the control member and to exert a pre-load on the clutch releasefork.

It will be appreciated that the cylinder and the piston are of simpleshape and that the receiver is axially compact. Finally, this solutionrequires a minimum number of joints, namely one joint per guidingprojection, so that a single joint is axially movable (the oneassociated with the piston).

Advantageously, the piston is in two parts, namely a tubular part (thepiston proper) and the guiding projection, the two being held togetherby a pre-loading spring acting on the control member in order to pushthe fork so that this exerts a pre-load on the clutch release bearing.By virtue of this arrangement, the piston is simply made from twomaterials, one of which is adapted for its guidance.

Advantageously, the cylinder of the receiver has a nose by means ofwhich it bears against its associated counter-support. The nose enableseasy mounting on its counter-support.

Thus the counter-support can consist of the sheath stop of aconventional cable control and advantageously the cylinder offers, byvirtue of its nose, a guiding area for its associated piston.

In order to facilitate mounting, to limit the movement of the piston andto protect the control chamber against the ingress of dust and othercontaminants, the cylinder is advantageously closed by a part attachedto the said cylinder (the bottom thereof) such that it is easy to effectthe mounting of the piston and of the associated end of the controlmember.

It will be appreciated that the cable control allows a better movementof the piston and reduces risks of jamming.

The description which follows illustrates the invention with referenceto the accompanying drawings, in which:

FIG. 1 is a schematic view of a piston clutch with its clutch releasefork controlled by a cable;

FIG. 2 is a view in section of a hydraulic control according to theinvention, the upper part of the figure corresponding to the retractedposition which the piston occupies when the clutch is disengaged, whilstthe lower part of this figure corresponds to the extracted positionwhich the piston occupies when the clutch is engaged;

FIGS. 3 and 4 are views identical to FIG. 2 of other exampleembodiments.

In the embodiment depicted in FIG. 2, which concerns, by way ofnon-limitative example, an application of the invention in a hydrauliccontrol circuit of a clutch of a motor vehicle, a master cylinder ofthis hydraulic circuit can be seen at 20. The master cylinder 20 has acylinder 22 and a piston 21 mounted sliding in the cylinder 22 anddefining in this cylinder a chamber of variable volume.

The piston 21 is controlled by control means, here a clutch pedal 24,mounted pivoting on a fixed part 36 of the vehicle. This piston 21 iscontrolled by means of a rod 23 connected to the clutch pedal 24.

In a variant, not depicted, the control means have an assistance deviceinterposed between the piston 21 and the clutch pedal 24 and controlledby the said pedal.

The master cylinder 20 is connected, in a manner known per se, to areservoir and constitutes a transmitter connected by a conduit 19 to ahydraulic receiver 1 according to the invention.

The receiver 1 has a cylinder 2 in which a piston 4 is engaged so as tobe able to slide. The piston 4 defines in the cylinder 2 a chamber 6 ofvariable volume, which is connected by an inlet 18 to the conduit 19 andmaster cylinder 20.

The piston 4 is subjected to the action of a return spring 7 and isadapted to act by pulling the clutch release fork 25 of FIG. 1 by meansof a control member 8 capable of acting in traction on the clutchrelease fork 25 by being mounted in an articulated manner on the saidfork 25 with the aid of a drive bearing 9.

The control member 8 is a cable acting between two bearings articulatedrespectively on the piston 4 and on the clutch release fork 25. Thismember is thus coupled to the piston 4 of the receiver 1, being mounted,according to one characteristic of the invention, so as to articulate onthe back face thereof.

Here, the cylinder 2 is mounted on a counter-support 5 fixed to a fixedpart of the vehicle, in this case the gearbox housing.

To this end, the cylinder 2 has at its front end a nose 12 penetratinginside its fixed, centrally perforated counter-support 5. This nose 12,of tubular shape, thus defines a shoulder 30 of roughly transverseorientation. This nose 12 passes through the aperture of thecounter-support 5 and has a groove for receiving a circlip 13, with aspacing washer 14 being interposed between the circlip 13 and thecounter-support 5.

Thus the counter-support 5 is sandwiched between the shoulder 30 and thewasher 14 so that the cylinder 2 is fixed on the fixed counter-support5.

It will be appreciated that the mounting of the cylinder 2 is effectedeasily simply by slipping axially into the aperture of thecounter-support 5 and locking by means of the circlip 13.

The cylinder 2 can thus be mounted in the sheath stop usually present onthe gearbox housing for mounting a cable control acting in traction onthe clutch release fork.

Thus the hydraulic control device according to the invention is mountedin place of a conventional cable control. Here, the cylinder 2 is oftubular shape and has a front face delimited by the internally borednose 12 and a back face closed by a closing cap 3 mounted by means ofsnap-in connection, or as a variant by screwing, on a tubular body 2 inone piece with the nose 12.

The body 2, of simple shape and made of mouldable material, isadvantageously made of plastic material with a low coefficient offriction so that the nose 12 offers internally a guide surface for thepiston 4. The body 2 constituting the cylinder 2 is internally steppedand thus has an internal bore with a change in diameter at its nose 12.

The piston 4 is of tubular shape and has a tubular part, here made ofmetal 4, guided by the nose 12 at one of its ends (its front end) and bya guiding part 15 at the other of its ends (its back end). For thispurpose, the back end of the tube 4 has a radial collar 32 for the axialretention of the part 15. A shouldered part 10, here made of plastic,rests on the back face, turned towards the cap 3, of the collar 32 andpenetrates inside the tube 4.

The part 10 to a certain extent constitutes a plug. This plug ishollowed centrally for the installation of a control bearing 11, here ofhemispherical shape. This bearing 11 is fixed to the cable 8 which,according to one characteristic of the invention, passes through thepiston 4.

The control member 8 is thus, according to the invention, coupled to therear, or back, end of the piston 4 via the part 10, being mounted in anarticulated manner on the said piston 4. The bearing 11 is thus inengagement with the part 10 cooperating with the back end of the piston4.

At its other end, the cable 8 is fixed to the bearing 9, also ofhemispherical shape. Naturally, the fork 25 is split locally for theinsertion (mounting) of the cable 8 in a conventional manner.

Thus the cable 8 enters inside the piston in order to act in traction onthe clutch release fork 25 when the chamber 6 is pressurised by means ofthe master cylinder 20 which is then subjected to the action of theclutch pedal, as seen in FIG. 2.

When the chamber 6 is depressurised, the piston 4, under the action ofthe load exerted by the diaphragm 27 of FIG. 1, occupies the positiondepicted in the lower part of FIG. 2, the spring 7 being compressed. Thechamber 6 is thus of annular shape, being delimited by two concentricparts, namely the piston 4 with its guide part 15 and the cylinder 2.Axially, the concentric chamber 6 is thus closed and delimited by thepart 15 and the nose 12. This chamber 6 extends axially on just one sidewith respect to the counter-support 5.

It will be noted that the nose 12 defines inside the cylinder 2 ashoulder 31 and that the hydraulic fluid inlet 18 is adjacent to thisshoulder 31.

The return spring 7, here a coil spring, bears on this fixed shoulder 31and on the axially movable guide part 15. Thus this spring 7 exerts apre-loading action on the fork 25 and on the clutch release bearing 26of FIG. 1. In addition, this spring 7, being of tapered shape, enablesthe two parts 4 and 15 of the piston to be connected together.

It will be noted that the part 15 is provided with shoulders in order toreceive the collar 32 of the tubular part 4.

Naturally, the sealing joints 16 and 17 are associated respectively withthe guide part 15 and the shoulder 31 of the nose 12 for the seatedmounting of the piston 4. Only the joint 16 is axially movable, thejoint 17 being carried by the fixed cylinder 2.

Thus the collar 32 of the tubular part 4 is sandwiched between the part10 and the part 15, being permanently wedged under the action of thespring 7.

The plastic part 15 thus slides along the larger-diameter internal boreof the piston 2. Here, this internal bore is formed by a metal tube 35moulded in one piece with the cylinder 2. Metal-on-plastic friction isthus obtained between the piston 4 and cylinder 2.

By virtue of these arrangements, an economical receiver of economicaland simple form is obtained, which is easy to mount as initially thepart 3 is not mounted and is not connected to the tubular cylinder 2until the end, just like the piston 4.

The cable 8 is thus mounted so as to articulate on the piston 4 at theback end thereof.

In a variant, the control member 8 consists of a rod mounted in anarticulated manner on the fork 25 and on the back end 32, 10 of thepiston 4 nearest the cap 3 by virtue of the bearings 9, 11.

The rod passes through the piston 4, being mounted in an articulatedmanner on the back face of the piston 4 and the fork 25 by virtue of thecontrol bearing 11 and drive bearing 9.

Thus, in all cases, when the piston 4 moves, a rectilinear movementthereof is obtained and a circular movement of the clutch release forkwithout the risk of jamming, the control member effecting a pendularmovement with small clearance when the piston moves. This movement isless pronounced than if the control member had been coupled to the frontend of the piston. It will be appreciated that the receiver 1 is axiallycompact by virtue of the projections 15, 12 and that only the joint 16is axially movable.

The part 10 constitutes a load transfer part. Preferably, it is piercedright through by at least one sloping channel, for the discharge of air.

As will have been understood, according to one characteristic of theinvention the piston 4 carries at its back end a guiding projection 15,whilst the cylinder has at its front end a guiding projection 12. Theguiding projection 15 of the piston 4 is directed radially outwards,whilst the guiding projection 12 is directed radially inwards. Theprojection 15 is capable of cooperating with the inner bore of thecylinder 2, whilst the projection 12 is capable of cooperating with theouter periphery of the piston 4.

The joint 16 is installed on a circumference of diameter greater thanthat on which the joint 17 is installed and this is the reason why thespring 7 is of tapered form.

Naturally, as seen in FIG. 3, the nose 12 can be extended at the frontby a tube 120 in order to protect the piston 4, having a guidingprojection 150 in one piece. Here the cylinder 2 is made of aluminiumand the return spring consists of a simple coil spring 70, the sealingjoints 160, 170 being mounted in grooves made respectively at the outerperiphery of the guiding projection 150 and at the inner periphery ofthe guiding nose 12 of the cylinder 2.

In this figure, the load transfer part 100 consists of a simple plate ofreduced thickness at its outer periphery for bearing on the back end ofthe piston 4. The plate 100 is centred by the piston 4 with a bevelledend.

The bearing 110 is spherical. In a variant, FIG. 4, the protection ofthe piston can be effected with the aid of a bellows 220 mounted on thenose 12 by resting and clamped onto the cable 8.

In this figure the inlet 18 is inclined.

It will be appreciated that the cap 3 serves as a stop for the loadtransfer part 10, 100 and thus limits the movement of the piston.

This cap 3 also has a protective role and prevents dirt, impurities orother substances from entering inside the cylinder 2.

Naturally, this cap 3 can be mounted by being screwed onto the cylinder2.

Generally, the cap 3 facilitates the mounting of the cylinder whilebeing installed last.

It will be appreciated that the guiding projection 12 of the cylinder 2is also used for fixing the receiver 1 to the counter-support 5 and thatthe return spring 7, 70, usually referred to as a pre-loading spring, ishoused in the chamber 6.

I claim:
 1. Hydraulic clutch control, having a clutch release fork (25)capable of being mounted pivoting on a fixed support, a control member(8) capable of acting in traction on the clutch release fork (25), beingmounted in an articulated manner on said fork by means of a drivebearing (9), a hydraulic receiver (1) having a fixed cylinder (2, 3)mounted on a counter-support (5) fixed to the fixed support and a piston(4, 10) engaged so as to slide sealingly in the cylinder (2, 3) anddefining therein a chamber (6) of variable volume connected to atransmitter (20) capable of being activated by a clutch pedal (24),characterized in that the cylinder (2) is of tubular shape, in that thepiston (4) is of tubular shape and carries at a back end a guidingprojection (15, 150) designed to cooperate with the internal bore of thecylinder (2) and directed radially outwards, whilst the cylinder (2) hasat a front end a guiding projection (12) designed to cooperate with theouter periphery of the piston (4) and directed radially inwards, and inthat the control member (8) enters inside the piston (4) of thehydraulic receiver (1) and is mounted at one of its ends in anarticulated manner on the clutch release fork (25) and at the other ofits ends so as to articulate on the back face of the piston (4) of thehydraulic receiver (1).
 2. Hydraulic clutch control according to claim1, characterized in that the control member (8) consists of a rodmounted in an articulated manner on the clutch release fork (25) and inan articulated manner on the back end of the piston (4).
 3. Hydraulicclutch control according to claim 1, characterized in that the controlmember (8) is a cable acting between two bearings (11, 9) coupledrespectively to the back end of the piston (4) and to the clutch releasefork (25).
 4. Hydraulic clutch control according to claim 1,characterized in that the cylinder (2) has a back face closed by aclosing cap (3) attached to the cylinder (2).
 5. Hydraulic clutchcontrol according to claim 4, characterized in that the front end of thecylinder (2) has a nose (12) by means of which the cylinder (2) bearsagainst its counter-support (5) fixed to a fixed part.
 6. Hydraulicclutch control according to claim 5, characterized in that the nose (12)offers a transverse shoulder (30) for its counter-support (5). 7.Hydraulic clutch control according to claim 6, characterized in that thecounter-support (5) is sandwiched between the shoulder (30) of the nose(12) and a thrust washer (13) fixed axially on the nose (12). 8.Hydraulic clutch control according to claim 5, characterized in that thenose (12) of the cylinder (2) constitutes the guiding projection for thepiston (4).
 9. Hydraulic clutch control according to claim 1,characterized in that the piston is in two parts and has a tubular guidepart (4) and a part (15) forming the guiding projection, held togetherby a pre-loading spring (7) bearing on a shoulder (31) formed by theguiding projection (12) of the cylinder (2) and on the guide part (15)in order to exert a pre-load on the control member (8) and in that thetubular part (4) has at its back end a collar (32) for retaining theguide part (15).
 10. Hydraulic clutch control according to claim 1,characterized in that the control member (8) is mounted so as toarticulate on the piston (4) by means of a bearing (11) in engagementwith a load transfer part (10, 100) cooperating with the back end of thepiston (4).